How to reduce tillage through diverse crop rotations
Conversations about tillage continue to be a hot topic in agriculture, and we have seen organic systems come under fire for their reliance on tillage compared to conventional, chemically based no-till systems.
However, there are good reasons for practicing responsible tillage — other than for preparing seed beds and killing weeds. When a properly diverse crop rotation with cover cropping is practiced in an organic system, tillage that does occur is done with a purpose, in ways that offset the physical impact with other benefits to the soil and cropping system. Opportunities to significantly reduce tillage also arise.
There are a handful of soil-building principles regarding tillage to abide by. A major goal of any organic rotation should be to keep the ground covered with living plants as much as possible. Fall tillage with bare soil exposed in the winter should be avoided. When tillage does occur, it should be done slower to lessen the negative impact on soil structure, with the intention of incorporating organic matter in the form of animal manure and/or green manure, and to keep residues on the surface. Do not work the soil when it is too wet, and do a good job of tilling the first time so that it does not have to be done over. Lastly, allow the soil to rest and regenerate by incorporating periods of one year or more without tillage into your rotation. Ideally, this would be done in combination with at least one substantial biomass green manure that overwinters and is allowed to grow into maturity. This is incredibly effective in building soil, controlling weeds, and managing fertility.
One barrier to building diverse crop rotations that is typical of conventional systems — but is now increasingly shared by organic producers — is the over-reliance on corn and soybeans in the rotation. Both crops create major challenges in terms of including cover crops in a rotation and reducing tillage in organic systems. However, marketing a more diverse crop rotation is a major concern. To overcome this barrier most readily, it is recommended to find an experienced organic grain marketer who will work hard to market your entire rotation, such as those from the OFARM network. Rodale Institute’s consulting department also has on staff a market coordinator who works to discover organic market opportunities, build relationships and connect producers with buyers. These are just a couple examples of the resources that are available. Also, don’t underestimate the value of networking and building relationships with other organic producers. Through a little determination, marketing a diverse rotation of crops can be accomplished and can make your system more profitable in the long term.
Supposing that the question of marketing can be answered, the challenge then often becomes what other crops to plant and how to sequence them effectively with corn and soybeans. To answer that question, we need to understand the impact that each potential crop and its management has in terms of ability to build soil tilth or take away from it. The topsoil building choices would be deep-rooted legumes such as alfalfa and sweet clover, followed by annual small grains and shallow-rooted legumes such as peas and clover. Solid-seeded broadleaves such as buckwheat and flax also contribute some to soil building. However, row crops that require cultivation — corn, soybeans, dry edible beans and vegetables such as potatoes, onions, carrots, etc. — are destructive of soil tilth and also often contribute to challenges with weed control and managing fertility. This must all be taken into account and balanced accordingly in order to have more years in the rotation that build soil than that take away, as well as to contribute to your ability to effectively control weeds and manage fertility. This usually means the incorporation of alfalfa hay or green-manure soil-building years into the rotation.
When thinking about the sequence of crops in a rotation, it is helpful to reduce potential crops to their season. There are cool season annuals, warm season annuals and winter annuals. To maximize soil-building and weed-suppression potential, each of those should be incorporated into a full rotation. It is also helpful to start writing a rotation with the soil-building green manure or alfalfa hay year(s) at the top. Proceeding from there, either the mature green manure or hay crop should ideally be terminated in late summer.
In keeping with the principal of living roots in the ground as often as possible, that should immediately be followed by a winter annual such as rye or triticale and a cover crop. The cover crop can be no-till drilled after harvest or often just be volunteers from the previous crop. That can be terminated in the spring and followed by a warm-season annual. Without a manure application, this could be soybeans or a small grain such as buckwheat.
Following the warm season annual would ideally be another soil-building green-manure year. For example, sweet clover could have been undersown in the previous warm season crop or sorghum sudangrass could be planted the following year. However, in systems that are more advanced, with a low weed seedbank and good weed control, it is also possible to follow with a manure application and one more warm-season annual — likely corn — before going back to a green manure.
After the green manure, fitting in a cool-season annual small grain such as wheat, oats, barley, etc. would be ideal, followed by either a volunteer or no-till-seeded cover crop. The following spring would then be another warm-season annual. If at this point in the rotation a manure application had not been made and no corn grown yet, then it would be advantageous to do so. A warm-season small grain such as millet could also be grown here, giving the opportunity to undersow sweet clover or alfalfa and avoid tillage before rolling back to the top of the rotation with another soil-building green manure or alfalfa hay crop year(s).
With this type of sequencing, even with tillage ahead of and following corn and soybeans, there are still three periods of over one year without tillage in the rotation. If cultivated row crops are eliminated from this scenario and only crops that contribute to building soil are grown, the full potential of diverse organic crop rotations in reducing tillage can be illustrated. Four different periods of more than one year without tillage would be achieved over the rotation. Only four tillage operations would be necessary over the course of at least six — but up to nine — years, and each one of those operations would be incorporating animal manure and/or green manure.
There are many different possible rotations that may work for any number of farmers, depending on their climate, soil and other factors, but this scenario gives a good framework to work from to fulfill the soil-building principles we should be striving to meet in our rotations.#
Nicholas Podoll is a Midwest Organic Consultant at the Rodale Institute. He has served as an extension agent and educator at North Dakota State and the University of Minnesota.
